Elevator Balance Issue

[cliffy]

Have a friend I'm talking with who has had a new paint job done and he says the elevators are way out of balance. He says the paint shop figures they need new balance weights that are 10 ounces heavier than the ones that came on the airplane. 49 ozs. vs 39 ozs. About a 25% increase in weight. 

This is a K model.

We've gone through all the normal stuff, stripped to bare metal, correct balance procedure, etc etc. I've never seen nor has anyone I have talked to seen a 10 oz weight difference after paint. Now the paint job is fantastic and they say they put 4 coats on the entire airplane. Maybe 4 coats on the elevators would do it.

At this rate maybe he needs to reweigh the entire airplane for the weight of the paint. :-) 

Has any of you ever seen this much weight change? I'm suspect of the figure they are touting. 

[jetdriven]

Read the service manual carefully. These elevators are often under balanced, IE, the trailing edge weighs 10-14oz when sitting on the jig and level.  

[takair]

2 hours ago, jetdriven said:

Read the service manual carefully. These elevators are often under balanced, IE, the trailing edge weighs 10-14oz when sitting on the jig and level.  

Agreed. Have seen people try to “balance” a surface, but it is not truly 1 to 1.  

Cliffy...did you actually see them do the balancing?

[takair]

Came across this other thread, so I know Cliff is familiar with the he procedure.....

 

[RLCarter]

3 hours ago, cliffy said:

At this rate maybe he needs to reweigh the entire airplane for the weight of the paint. :-)

I think a new weight n balance is required after re-painting 

[jetdriven]

Balanced control surfaces are required after painting.  

[Yetti]

The factory put on a very very very thin coat of paint.  Pretty sure paint had lots of bad chemicals in it that made it last a long time.   44 years this month in my planes case.   Just needed a buffing when I got it.

[211º]

A thought experiment...

If I remember the figures correctly, the space shuttle saved about 400 pounds when they stopped painting the external tank. I think that American plans are also lighter because of no-paint.

My brain wanders to “how much paint was sprayed on the surface during each coat” - meaning “how much did ‘the guy’ spraying actually go through with each coat? Could he have done one coat with about 1/3 of a cup of paint?”

[mike_elliott]

Cliff,  It is the consensus of Joe Dinolfo (Hawk aircraft painting) that Russell Kelly's plane either 1) Had a ton of bondo on the elevator that was stripped off or 2) the paint shop needs to refigure the balance. He has done a number of Mooneys and never has seen one that needed anywhere close to 10 oz. I passed this info onto Pieter Mol also.

 

[carusoam]

This balance issue has come up before as well....

Rob has captured the thread....(above)

 

The paint shop is probably using a good procedure, but the Mooney numbers would need to be adjusted to the procedure...?

 

This is an Old Fuzzy memory... but it stands out.  An MSer had perfect sheet metal on their flight controls, but couldn’t get close to getting balanced...

Essentially, I am saying research the right procedure, if the balance is that far off....

PP thoughts only, not a mechanic...

Best regards,

-a-

[cliffy]

Mike- Thanks for your input and effort.

I didn't know the problem had made it this far yet. I tossed the question out as I had never seen anything close to 10 oz. needed between one paint job and another. It doesn't pass the smell test to me. 

As to the bondo, If it was removed and not replaced that would make the balance weight lighter not heavier, I would think, as the bondo would be behind the hinge line. 

I asked how the other surfaces came out but have not heard back yet. If they had no issue with rebalance on them then I told Russ that I'm still skeptical of the procedure and not the surface. 

I suggested that they really review the manual to make sure they were using the correct one and not from another model Mooney as the balance limits change from model and production block number quiet often even in the same model. Can't use a J model balance limit on a K model. I think Pieter Mol is pretty sharp but I also think something is being missed. Its all coming to Pieter from the pint shop. They, not him, are doing the balance. I don't know anything about the paint shop or their experience with Mooneys. I've asked for the torque figures the paint shop has come up with. I'm thinking they are going for perfect balance and not the underbalance called for in the manual. I'd like to see the torque figures. I'd prefer to see a picture of the balance rig with the elevator in it. Don't know if they have the control horn on or off during the weigh either. 

I have seen 1 -3 ozs on other airplanes at times but not 10 oz. Some people have actually used slugs of depleated uranium to balance as its heavier than lead. 

Thanks again. Story to continue after the holidays as the factory is closed. 

[Guest]

8 hours ago, cliffy said:

Have a friend I'm talking with who has had a new paint job done and he says the elevators are way out of balance. He says the paint shop figures they need new balance weights that are 10 ounces heavier than the ones that came on the airplane. 49 ozs. vs 39 ozs. About a 25% increase in weight. 

This is a K model.

We've gone through all the normal stuff, stripped to bare metal, correct balance procedure, etc etc. I've never seen nor has anyone I have talked to seen a 10 oz weight difference after paint. Now the paint job is fantastic and they say they put 4 coats on the entire airplane. Maybe 4 coats on the elevators would do it.

At this rate maybe he needs to reweigh the entire airplane for the weight of the paint. :-) 

Has any of you ever seen this much weight change? I'm suspect of the figure they are touting. 

Cliff,

Here is the flight control balance section from the manual.

Clarence

[cliffy]

ThnX for the doc  I don't have a copy close at hand right now.